若x=1,y=2,求1/(x+y)+1/(x-y)+2x/(x^2+y^2)+4x^3/(x^4+y^4)的值!把数往里带我也会啊,可是老师说要化简的…我凌乱了…各位帮帮忙
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若x=1,y=2,求1/(x+y)+1/(x-y)+2x/(x^2+y^2)+4x^3/(x^4+y^4)的值!
把数往里带我也会啊,可是老师说要化简的…我凌乱了…各位帮帮忙
先化简,前两个分式先通分,即1/(x+y)+1/(x-y)通分,得到2x/(x^2-y^2);
再将得到的式子与第三个分式,即2x/(x^2+y^2),相加,先提取公因式2x再通分得到:4x^3/(x^4-y^4);
再将得到的式子与第四个分式,即4x^3/(x^4+y^4),相加,先提取公因式4x^3再通分得到:8x^7/(x^8-y^8);
最后,再将x=1,y=2代入上式,得到最终结果-8/255
希望对你有用
我知道了加我Q吧。1755694803 我发不出来
将x=1,y=2,代入就行了!我算出来是8/225
接着代入数据即可。
^什么意思
带入运算 1/(1+2)+1/(1-2)+2*1/(1+4)+4*1/(1+16)= -8/255
具体步骤,一步一步推得
1/x+y+1/x-y+2x/(x^2+y^2)+4x^3/(x^4+y^4)
=x-y+x+y/(x+y)(x-y)+2x/(x^2+y^2)+4x^3/(x^4+y^4)
=2x/x^2-y^2+2x/(x^2+y^2)+4x^3/(x^4+y^4)
=4x^3/(x^2)^2-(y^2)^2+4x^3/x^4+y^4
=4x^3/x^4-y^4+4x^3/x^4+y^4
=8x^7/x^8-y^8
x=1,y=2
∴原式=-8/225
望采纳!!
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